Stack mold linkage with unequal strokes

Abstract

The present invention relates to stack mold linkages for creating unequal strokes for use in an injection molding machine for making different sized molded parts. The stack mold linkages comprise linkages for moving each of at least two mold assemblies between a mold closed position and a mold open position and for separating the mold halves forming the mold assemblies by unequal stroke lengths.

What is claimed is: 
     
       1. An injection molding machine comprising: a stationary platen and at least two members movable relative to said stationary platen;   at least two mold assemblies formed by mold halves attached to said stationary platen and said two movable members;   means for moving each of said at least two mold assemblies between a mold closed position and a mold open position; and   said moving means including means for separating the mold halves forming said mold assemblies by unequal stroke distances.   
     
     
       2. Machine according to claim 1, wherein said separating means comprises first means for separating the mold halves of a first one of said mold assemblies by a first stroke distance and second means for separating the mold halves of a second one of said mold assemblies by a second stroke distance, which second stroke distance is greater than said first stroke distance. 
     
     
       3. Machine according to claim 2 further comprising means for actuating said second means when one of said movable members reaches a preselected position. 
     
     
       4. Machine according to claim 2, wherein: said two movable members include a central section carrier and a movable platen;   said first means comprising a linkage assembly pivotally connected to said central section carrier; and   said second means comprising a rotatable link arm mounted to said movable platen and connected to said linkage assembly.   
     
     
       5. Machine according to claim 4, further comprising means for causing said rotatable link arm to rotate when said movable platen has reached a preselected position. 
     
     
       6. Machine according to claim 5, wherein said means for causing said rotatable link arm to rotate comprises an actuation cylinder mounted to said movable platen. 
     
     
       7. Machine according to claim 4, wherein: said linkage assembly comprises a central link pivotably connected to said central section carrier and a first link arm connected to a first end of said central link and to said stationary platen; and   said second means further comprises a second link arm connected to a second end of said central link and to said rotatable link arm.   
     
     
       8. Machine according to claim 7, wherein said second link arm is pivotally connected to said rotatable link arm so that said second link arm and the rotatable link arm can change their angular relationship to each other. 
     
     
       9. Machine according to claim 8, further comprising: said rotatable link arm having a plurality of spaced slots for changing the distance said movable platen can travel; and   said second arm being connected to said rotatable link arm by a pin which passes through one of said slots.   
     
     
       10. Machine according to claim 2, further comprising: a plurality of tiebars;   said movable members comprising a central section carrier and a movable platen;   said first means comprising a linkage assembly connected to said central section carrier; and   said second means comprising a bracket member connected to said linkage assembly and means for releasably clamping said bracket member to said movable platen.   
     
     
       11. Machine according to claim 10, wherein said releasable clamping means is operated to release said bracket member when said movable platen reaches a preselected position. 
     
     
       12. Machine according to claim 10, further comprising: said linkage assembly including a central link connected to said central carrier and a first link arm connected to a first end of said central link and to said stationary platen;   said second means further comprising a second link arm connected to a second end of said central link and to said bracket member; and   a movable frame attached to said second link arm for carrying an end thereof.   
     
     
       13. Machine according to claim 2, wherein: said movable members comprise a movable platen and a central section carrier;   said first means comprises a linkage assembly connected to said central section carrier; and   said second means comprises a bar attached to said linkage assembly, said bar being slidably mounted to said movable platen.   
     
     
       14. Machine according to claim 13, wherein said second means further comprises an actuation unit and first and second links each connected to said actuation unit and to said bar and wherein said actuation means causes relative movement between said bar and said movable platen when said movable platen reaches a preselected position. 
     
     
       15. Machine according to claim 13, wherein said linkage assembly comprises a central link connected to said central carrier and a first link arm connected to said stationary platen and to a first end of said central link, and said second means further comprises a second link arm connected to a second end of said central link and to an end of said bar. 
     
     
       16. Machine according to claim 2, wherein: said movable members comprises a central section carrier and a movable platen;   said first means comprises a linkage assembly connected to said central section carrier; and   said second means comprising a bar connected to said linkage assembly, said bar and said movable platen being movable relative to each other.   
     
     
       17. Machine according to claim 16, further comprising: said bar having a recess; and   said movable platen having a locking means for securing said bar in a fixed position relative to said movable platen by engagement with said recess.   
     
     
       18. Machine according to claim 17, wherein said locking means disengages from said recess when said movable platen reaches a preselected position, thereby allowing relative movement between said movable platen and said bar. 
     
     
       19. Machine according to claim 18, further comprising: means for causing relative movement between said bar and said movable platen when said movable platen reaches a preselected position.   
     
     
       20. Machine according to claim 19, wherein said relative movement causing means comprises an actuation unit connected to said movable platen and at least one link connected to said bar and said actuation unit. 
     
     
       21. Machine according to claim 19, wherein said relative movement causing means comprises an actuation unit connected to said movable platen and first and second link arms, each of said link arms being connected to said actuation unit at one end and to said bar at a second end. 
     
     
       22. Machine according to claim 16, wherein said linkage assembly comprises a central link pivotally connected to said central section carrier and a first link arm connected to said stationary platen and to a first end of said central link and said second means further comprises a second link arm connected to a second end of said central link and to an end of said bar. 
     
     
       23. Machine according to claim 1, wherein: said movable members comprise a central section carrier and a movable platen; and   said separating means comprises a channel member pivotally connected to said central section carrier at a pivot point, a center arm positioned within said channel member and being movable relative to said channel member so that the distance between its ends and said pivot point can be changed, a first link arm attached to one end of said center arm and said stationary platen and a second link arm attached to a second end of said center arm and said movable platen.   
     
     
       24. Machine according to claim 23, wherein said center arm has a plurality of slots for allowing the position of said center arm relative to said channel member to be changed. 
     
     
       25. Machine according to claim 24, further comprising pins for securing said center arm in a desired position relative to said channel member, said pins passing through at least two of said slots. 
     
     
       26. Machine according to claim 2, further comprising: said machine having four movable members including two central section carriers and two movable platens;   said first means comprising a linkage assembly pivotally connected to each of said central section carriers; and   said second means comprising a rotatable link arm mounted to each of said movable platens and connected to a respective one of said linkage assemblies.   
     
     
       27. Machine according to claim 26, further comprising actuation means for causing each said rotatable link arm to rotate when said movable platen to which it is connected has reached a preselected position. 
     
     
       28. Machine according to claim 27, wherein said actuation means for causing each said rotatable link arm to rotate comprises an actuation cylinder mounted to each said movable platen. 
     
     
       29. Machine according to claim 26, wherein: each said linkage assembly comprises a central link pivotably connected to a respective one of said central section carriers and a first link arm connected to a first end of said central link and to said stationary platen; and   said second means further comprises a second link arm connected to a second end of said central link and to said rotatable link arm.   
     
     
       30. Machine according to claim 29, wherein each said second link arm is connected to a respective one of said rotatable link arms so that said second link arm and the rotatable link arm can change their angular relationship relative to each other. 
     
     
       31. Machine according to claim 1, further comprising: four movable members including two central section carriers and two movable platens;   four mold assemblies formed by mold halves attached to said stationary platen, said central section carriers and said movable platens;   said separating means comprising a plurality of racks attached to said stationary platen and said movable platens, gear means mounted to said central section carriers for engaging said plurality of racks, and a linkage assembly pivotably mounted to said stationary platen;   said linkage assembly being rotatably mounted to said stationary platen and having a first link arm connected to a first one of said gears and a second link arm connected to a second one of said gears, said second link arm being longer than said first link arm, whereby rotation of said linkage assembly causes two of said mold assemblies to be separated by a first stroke distance and causes the remaining two of said mold assemblies to be separated by a second stroke distance greater than said first stroke distance.   
     
     
       32. Machine according to claim 31, wherein said gear means comprises two gears, and one of said gears having a larger diameter than the other of said gears. 
     
     
       33. Machine according to claim 31, wherein said linkage assembly includes a central link member rotatably mounted to said stationary platen and each of said first and second link arms being connected to a respective end of said central link member. 
     
     
       34. A method for fabricating molded articles using a single molding machine comprising the steps of: providing an injection molding machine having a stationary platen and at least two members movable relative to said stationary platen and further having at least two mold assemblies formed by mold halves attached to said stationary platen and said at least two movable members;   injecting a material into each of said mold assemblies while said assemblies are each in a mold closed position to form said articles;   moving each of said mold assemblies between said mold closed position and a mold open position where said molded articles are ejected from the machine; and   said moving step comprising separating the mold halves forming a first mold assembly by a first stroke distance and separating said mold halves forming a second mold assembly by a second stroke distance larger than said first stroke distance.   
     
     
       35. Method according to claim 34, wherein said moving step comprises separating said mold halves forming a first mold assembly at a rate of speed different from the rate of speed used to separate said mold halves forming said second mold assembly. 
     
     
       36. Method according to claim 34, wherein said step of separating said mold halves forming a second mold assembly a second stroke distance comprises actuating means for increasing the stroke distance when one of said at least two movable members reaches a preselected position. 
     
     
       37. Method according to claim 36, wherein said actuating step comprises actuating a rotatable link mounted to said one movable member to increase said stroke distance. 
     
     
       38. Method according to claim 36, further comprising: providing a rotatable linkage assembly attached to a first one of said movable members and a bracket member connected to said linkage assembly;   providing means for clamping said bracket member to a second one of said movable members; and   said actuating step comprising releasing said bracket member to increase said stroke distance.   
     
     
       39. Method according to claim 36, further comprising: providing a rotatable linkage assembly mounted to a first one of said movable members and a slide bar mounted to said linkage assembly; and   said actuating step comprising moving said slide bar relative to a second one of said movable members so as to increase said stroke distance.   
     
     
       40. Method according to claim 36, further comprising: providing a rotatable linkage assembly mounted to a first one of said movable members and a slide bar having a recess mounted to said linkage assembly;   providing a locking unit mounted to a second one of said movable members for engaging said recess; and   said actuating step comprising releasing said locking unit from engagement with said recess so that said slide bar can move relative to said second one of said movable members and thereby increase the stroke distance.   
     
     
       41. Method according to claim 34, further comprising: mounting a channel member on one of said stationary platen and said movable members;   providing a center arm member having two link arms attached to its ends;   attaching said link arms to the others of said stationary platen and said movable members; and   adjusting said center arm member relative to said channel member so as to separate the mold halves forming the first mold assembly by said first stroke distance and the mold halves forming the second mold assembly by said second stroke distance.   
     
     
       42. Method according to claim 34, wherein said step of providing an injection molding machine comprising providing an injection molding machine having said stationary platen and four movable members and further having four mold assemblies formed by said mold halves attached to said stationary platen and said movable members. 
     
     
       43. Method according to claim 42, further comprising: mounting rack means on said stationary platen and on first and second ones of said movable members;   mounting gear means on third and fourth one of said movable members to engage said rack means;   mounting a linkage assembly to said stationary platen, said linkage assembly having a first arm of a first length connected to a first one of said gear means and a second arm of a second length connected to a second one of said gear means, said second length being greater than said first length; and   said moving step comprising actuating said linkage assembly so as to separate two of said mold assemblies by said first stroke distance and to separate two of said mold assemblies by said second stroke distance.   
     
     
       44. Method according to claim 42, wherein said moving step comprises: mounting a rotatable arm member to a first one and a second one of said movable members;   connecting each of said rotatable arm members to a rotatable linkage connected to one of a third one and a fourth one of said movable members; and   actuating each of said rotatable members when said first and second movable members reach a preselected position to cause two of said mold assemblies to separate by said second stroke distance.